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udp broadcast accross IPSec over PIX


I have established a IPSec Tunnel between a Cisco uBR and a PIX firewall.

I am able to reach(ping) the hosts on both the sides.

Now I have a udp broadcast traffic from the PIX side to be transported to the ubr side, which is not happenning.

I am using PIX software OS 6.2

I believe Cisco PIX doesn't forward any broadcast traffic...

So the only option here is to use GRE tunnel.....but again I believe you cannot terminate GRE tunnel on the PIX firewall.

What should be the solution in this case to carry udp broadcast traffic??

Will PIX support broadcast in its future release?

A sample config. will be very helpful.

thanks and Rds

Cisco Employee

Re: udp broadcast accross IPSec over PIX


You are 100% on your analysis of the PIX not having support for the GRE and that being a solution in this case. One other thing you can turn to is to terminate the GRE tunnel somewhere behind the PIX on another Router to the ubr Router, that way the GRE packets would be encrypted till the PIX Firewall and then be delivered to the inside Router where they will get decapsulated from the GRE packet and your udp broadcast would get through.

There are currently no plans to support GRE on the PIX Firewall anytime soon.

The following link shows GRE config and packets going through the PIX, (although it also has the IPSec config on the Routers, which you don't need):

Hope this helps,


Aamir Waheed,

Cisco Systems, Inc.



Re: udp broadcast accross IPSec over PIX


I have put another uBR behind the PIX and terminating the GRE tunnel on the this uBR. Well I am able to get the UDP broadcast now...

I also need to do this with Cisco VPN Client instead of the uBR......

How do I receive udp broadcast with VPN client??.....Because I will be terminating the IPSec tunnel on the PIX firewall..

Let me know..


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